WO2005121705A1 - Built in test for mems vibratory type inertial sensors - Google Patents
Built in test for mems vibratory type inertial sensors Download PDFInfo
- Publication number
- WO2005121705A1 WO2005121705A1 PCT/US2005/020234 US2005020234W WO2005121705A1 WO 2005121705 A1 WO2005121705 A1 WO 2005121705A1 US 2005020234 W US2005020234 W US 2005020234W WO 2005121705 A1 WO2005121705 A1 WO 2005121705A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- test signal
- signal
- motor drive
- inertial sensor
- component
- Prior art date
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
- G01C19/56—Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
- G01C19/5719—Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces using planar vibrating masses driven in a translation vibration along an axis
Definitions
- This invention relates generally to MEMS vibratory type inertial sensors such as MEMS gyros and MEMS accelerometers, and more specifically to MEMS vibratory inertial sensors with build in test.
- MEMS vibratory type inertial sensors are used in a wide variety of applications. For many of these applications, a high degree of reliability is desired. For example, in automotive stability control systems, reliable inertial sensors are desirable to reduce erroneous or misleading data, which in some cases, could lead to loss of control of the automobile. What would be desirable is a MEMS vibratory type inertial sensor that has some level of built in test to help improve the reliability by helping to identify erroneous or misleading data provided by the inertial sensor.
- the present invention provides a MEMS vibratory type inertial sensor that has some level of built in test to help improve the reliability by helping to identify erroneous or misleading data provided by the inertial sensor.
- a test signal is injected into one or more of the inputs of the MEMS vibratory type inertial sensor, where the test signal produces a test signal component at one or more of the MEMS vibratory type inertial sensor outputs.
- the test signal component is then monitored at one or more of the outputs. If the test signal component matches at least predetermined characteristics of the original test signal, it is more likely that the MEMS vibratory type inertial sensor is operating properly and not producing erroneous or misleading data.
- the test signal is provided and monitored during the normal functional operation of the MEMS vibratory type inertial sensor, thereby providing on-going built in test.
- Figure 1 is a schematic view of a MEMS-type gyroscope in accordance with the present invention.
- Figure 2 is a schematic view of an illustrative MEMS-type gyroscope with a level of build in test.
- MEMS-type gyroscope 10 For illustrative purposes, and referring to Figure 1 , a MEMS-type gyroscope 10 will be described in detail. However, it should be recognized that the present invention can be applied to a wide variety of MEMS vibratory type inertial sensors such as MEMS gyros and MEMS accelerometers, as desired.
- Gyroscope 1 illustratively a vibratory rate gyroscope, includes a first proof mass 1 2 and second proof mass 14, each of which are adapted to oscillate back and forth above an underlying support substrate 1 6 in a drive plane orthogonal to an input or "rate" axis 1 8 of the gyroscope in which inertial motion is to be determined.
- the first proof mass 1 2 can be configured to oscillate back and forth above the support substrate 16 between a first shuttle mass 22 and first drive electrode 24, both of which remain stationary above the support substrate 16 to limit movement of the first proof mass 12.
- the second proof mass 14 in turn, can be configured to oscillate back and forth above the support substrate 1 6 in a similar manner between a second shuttle mass 26 and second drive electrode 28, but in most cases 1 80° degrees out-of-phase with the first proof mass 1 2, as indicated generally by the left/right set of arrows 30.
- the first proof mass 1 2 can include a thin plate or other suitable structure having a first end 32, a second end 34, a first side 36, and a second side 38. Extending outwardly from each end 32,34 of the first proof mass 12 are a number of comb fingers 40,42. Some of the comb fingers can be used to electrostatically drive the first proof mass 1 2 in the direction indicated by the right/left set of arrows 20. In the illustrative gyroscope 1 0 depicted in Figure 1 , for example, a first set of comb fingers 40 extending outwardly from the first end 32 of the first proof mass 1 2 can be interdigitated with a corresponding set of drive comb drive fingers 44 formed on the first drive electrode 24.
- the set of comb fingers 46 may be used to sense the motion of the first proof mass 1 2.
- the second proof mass 14 can be configured similar to the first proof mass 1 2, having a first end 48, a second end 50, a first side 52, and a second side 54.
- a first set of comb fingers 56 extending outwardly from the first end 48 of the second proof mass 16 can be interdigitated with a corresponding set of comb fingers 58 formed on the second shuttle mass 26.
- the set of comb fingers 58 may be used to sense the motion of the second proof mass 1 4.
- a second set of comb fingers 60 extending outwardly from the second end 50 of the second proof mass 1 4, in turn, can be interdigitated with a corresponding set of drive comb fingers 62 formed on the second drive electrode 28.
- the first and second proof masses 1 2,14 can be constrained in one or more directions above the underlying support structure 1 6 using one or more suspension springs.
- the first proof mass 1 2 can be anchored or otherwise coupled to the support substrate 1 6 using a first set of four suspension springs 64, which can be connected at each end 66 to the four corners of the first proof mass 1 2.
- the second proof mass 14 can be anchored to the underlying support substrate 1 6 using a second set of four springs 68, which can be connected at each end 70 to the four corners of the second proof mass 1 4.
- the suspension springs 64,68 can be configured to isolate oscillatory movement of the first and second proof masses 1 2,14 to the direction indicated generally by the right/left set of arrows 20,30 to reduce undesired perpendicular motion in the direction of the rate axis 1 8, and to reduce quadrature motion in the direction of the sensing motion 72.
- the suspension springs 64,68 can also be configured to provide a restorative force when the drive voltage signal passes through the zero point during each actuation cycle.
- a drive voltage V ⁇ can be applied to the first and second drive electrodes 24,28, inducing an electrostatic force between the interdigitated comb fingers that causes the comb fingers to electrostatically move with respect to each other.
- the drive voltage VD can be configured to output a time-varying voltage signal to alternate the charge delivered to the comb fingers, which in conjunction with the suspension springs 64,68, causes the first and second proof masses 1 2,14 to oscillate back and forth in a particular manner above the support substrate 16.
- the drive voltage VD WUI have a frequency that corresponds with the resonant frequency of the first and second proof masses 1 2,14 (e.g. 1 0 KHz), although other desired drive frequencies can be employed, if desired.
- a pair of sense electrodes 74,76 can be provided as part of the sensing system to detect and measure the out-of-plane deflection of the first and second proof masses 12,14 in the sense motion direction 72 as a result of gyroscopic movement about the rate axis 1 8.
- the illustrative sense electrodes 74,76 can include a thin, rectangular (or other) shaped electrode plate positioned underneath the proof masses 1 2,14 and oriented in a manner such that an upper face of each sense electrode 74,76 is positioned vertically adjacent to and parallel with the underside of the respective proof mass 1 2,14.
- the sense electrodes 74,76 can be configured in size and shape to minimize electrical interference with the surrounding comb fingers 40,42,56,60 to prevent leakage of the drive voltage source VD into the sense signal.
- a sense bias voltage Vs applied to each of the sense electrodes 74,76 can be utilized to induce a charge on the first and second proof masses 1 2,14 proportional to the capacitance between the respective sense electrode 74,76 and proof mass 1 2,1 4.
- the sense electrode 74,76 and the first and second proof masses 1 2,14 preferably include a conductive material (e.g. a silicon-doped conductor, metal or any other suitable material), allowing the charge produced on the sense electrode 74,76 vis-a-vis the sense bias voltage Vs to be transmitted to the proof mass 1 2,14.
- A is the overlapping area of the sense electrode and proof mass
- Vs is the sense bias voltage applied to the sense electrode
- eo is the dielectric constant of the material (e.g. vacuum, air, etc.) between the sense electrodes and the proof masses
- D is the distance or spacing between the sense electrode 74,76 and respective proof mass 1 2,14.
- the resultant charge received on the proof mass 1 2,14 may be fed through or across the various suspension springs 64,68 to a number of leads 78.
- the leads 78 can be electrically connected to a charge amplifier 80 that converts the charge signals, or currents, received from the first and second proof masses 1 2,14 into a corresponding rate signal 82 that is indicative of the Coriolis force.
- the sense bias voltage Vs applied to the first proof mass 1 2 can have a polarity opposite to that of the sense bias voltage Vs applied to the second proof mass 1 4.
- a sense bias voltage Vs of +5V and -5V, respectively can be applied to each of the sense electrodes 74,76 to prevent an imbalance current from flowing into the output node 84 of the charge amplifier 80.
- a relatively large value resistor 86 can be connected across the input 88 and output nodes 86 of the charge amplifier 80, if desired.
- a motor bias voltage VDC can be provided across the first and second shuttle masses 22,26 to detect and/or measure displacement of the proof masses 1 2,14 induced via the drive voltage source VD.
- a motor pickoff voltage VPICK resulting from movement of the comb fingers 42,56 on the first and second proof masses 12,14 relative to the comb fingers 46,58 on the first and second shuttle masses 22,26 can be used to detect/sense motion of the first and second proof masses 12,14.
- Figure 2 is a schematic view of an illustrative MEMS-type gyroscope with a certain level of build in test. The gyroscope of Figure 1 is shown in block form as gyro block 10.
- a drive oscillator 100 receives the motor pickoff voltage VPI C K discussed above with respect to Figure 1 . While only one motor pickoff voltage is shown in Figure 2, it is contemplated that in some embodiments, the drive oscillator 100 may be configured to receive a motor pickoff voltage Vp ⁇ c ⁇ rom each of the proof masses of Figure 1 . However, for simplicity, the embodiment shown in Figure 2 only shows and discusses the operation of one of the proof masses.
- the drive oscillator 100 uses the motor pickoff voltage VPICK to provide the next drive motor cycle.
- the drive motor signal can be configured to output a time-varying voltage signal to alternate the charge delivered to the comb fingers, which in conjunction with the suspension springs 64,68, causes the first and second proof masses 12,14 to oscillate back and forth in a particular manner above the support substrate 16 (see Figure 1 ).
- the drive voltage VD WMI have a frequency that corresponds with the resonant frequency of the first and second proof masses 1 2,14 (e.g. 10 KHz), although other desired drive frequencies can be employed, if desired.
- the output of the drive oscillator 100 may be provided to an amplitude controller 102.
- the amplitude controller 102 receives a reference amplitude from reference 1 04.
- the output of the amplitude controller 1 02 may be provided directly as the drive voltage VD to one of the proof masses.
- the output of the amplitude controller 102 may be provided to a modulator 105, which modulates the output of the amplitude controller 102 and a test signal 106.
- the test signal 106 may be a continuously running built in test (CBIT) AC signal, and may have a frequency that is substantially higher or substantially lower than the motor drive resonance frequency.
- the test signal 1 06 has a frequency of 50Hz and the motor drive signal has a frequency of about 1 OKHz, however other frequencies may be used.
- the amplitude of the test signal 1 06 may be made to substantially match an expected coriolis rate voltage (e.g. VRATE 82), but this is not required in all embodiments [Para 24] After the test signal 1 06 is modulated by modulator 1 05, the result is provided to the gyro 1 0 as the drive voltage VD.
- an expected coriolis rate voltage e.g. VRATE 82
- the drive voltage VD thus has a component that corresponds to the test signal 106 and a component that corresponds to the output of the amplitude controller 1 02.
- the component of the drive voltage VD that corresponds to the test signal 1 06 preferably has a frequency that is sufficiently off any resonant modes of the proof masses such that it has little or no effect on the electrostatic drive of the proof masses. However, in the illustrative embodiment, it is capacitively coupled to the proof masses (and in some cases to the sense plates), and ultimately to the charge amplifier 80, which converts the charge signals, or currents, received from the first and second proof masses 1 2,14 into a corresponding rate signal 82 that is indicative of the Coriolis force.
- the output 82 of the charge amplifier 80 may includes a component that corresponds to the experienced Coriolis force and a component that corresponds to the capacitively coupled test signal 106.
- the output 82 of the charge amplifier 80 may be provided to a rate amplifier 1 10, which amplifies the signal.
- the output of the rate amplifier 1 10 may be provided to a filter amplifier 1 1 2, which performs both a filtering and amplifying function.
- the output of the filter amplifier 1 1 2 may then be demodulated using the output of the amplitude controller 104, as shown at 1 14.
- test signal 1 06 is originally modulated using the output of the amplitude controller 104 as a reference, and the output of the filter amplifier 1 1 2 is demodulated using the same signal, as indicate by dashed line 1 16. This may help keep the modulated test signal 1 06 relatively in phase with the rate signal 82 that is indicative of the Coriolis force.
- the demodulated signal is provided to another filter amplifier 1 20, and the result is a DC rate bias signal with a superimposed component of the test signal, as shown at 1 22.
- This signal is passed to yet another filter 1 30 that separates the component of the test signal from the DC rate bias signal. If the component of the test signal 1 34 matches at least selected characteristics of the original test signal 106, it is more likely that the gyro 1 0 is operating properly and not producing erroneous or misleading data.
- the filter 1 30 may be simply a high pass filter and a low pass filter.
- a high pass filter may pass the component of the test signal 1 34 while the low pass filter may pass the DC rate bias signal 1 32.
- the filter 1 30 may be a more sophisticated filter, such as an adaptive filter.
- an adaptive filter is described in U.S. Patent No. 5,331 ,402, which is assigned to the assignee of the present invention.
- the adaptive filter may receive the original test signal 1 06 to help separate the component of the test signal 1 34 from the DC rate signal 1 32.
- the adaptive filter may be configured to "adapt" relatively slowly relative to the expected rate of change of the DC rate signal 1 32.
- the adaptive filter may have a time constant of 60 seconds, or any other suitable time constant as desired.
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Gyroscopes (AREA)
Abstract
Description
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Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP05759679A EP1761739A1 (en) | 2004-06-08 | 2005-06-08 | Built in test for mems vibratory type inertial sensors |
JP2007527709A JP2008501981A (en) | 2004-06-08 | 2005-06-08 | Built-in test for MEMS vibration type inertial sensor |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US57809704P | 2004-06-08 | 2004-06-08 | |
US60/578,097 | 2004-06-08 | ||
US11/160,062 | 2005-06-07 | ||
US11/160,062 US20050268716A1 (en) | 2004-06-08 | 2005-06-07 | Built in test for mems vibratory type inertial sensors |
Publications (1)
Publication Number | Publication Date |
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WO2005121705A1 true WO2005121705A1 (en) | 2005-12-22 |
Family
ID=35446220
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US2005/020234 WO2005121705A1 (en) | 2004-06-08 | 2005-06-08 | Built in test for mems vibratory type inertial sensors |
Country Status (4)
Country | Link |
---|---|
US (1) | US20050268716A1 (en) |
EP (1) | EP1761739A1 (en) |
JP (1) | JP2008501981A (en) |
WO (1) | WO2005121705A1 (en) |
Families Citing this family (17)
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EP1959233A1 (en) * | 2007-02-13 | 2008-08-20 | STMicroelectronics S.r.l. | Microelectromechanical gyroscope with self-test function and control method of a microelectromechanical gyroscope |
EP1962054B1 (en) * | 2007-02-13 | 2011-07-20 | STMicroelectronics Srl | Microelectromechanical gyroscope with open loop reading device and control method of a microelectromechanical gyroscope |
US20090241634A1 (en) * | 2008-03-28 | 2009-10-01 | Cenk Acar | Micromachined accelerometer and method with continuous self-testing |
US20100145660A1 (en) * | 2008-12-08 | 2010-06-10 | Robert Bosch Gmbh | Mems sensor with built-in self-test |
IT1397594B1 (en) * | 2009-12-21 | 2013-01-16 | St Microelectronics Rousset | MICROELETTROMECHANICAL GYROSCOPE WITH CONTINUOUS SELF-TEST FUNCTION AND METHOD OF CONTROL OF A MICROELECTRANOMIC GYROSCOPE. |
GB201003539D0 (en) | 2010-03-03 | 2010-04-21 | Silicon Sensing Systems Ltd | Sensor |
CN102893128B (en) | 2010-03-17 | 2016-02-17 | 大陆-特韦斯贸易合伙股份公司及两合公司 | The decoupling control method of the orthogonal and resonant frequency of micro-mechanical gyroscope |
KR101803990B1 (en) * | 2010-03-17 | 2017-12-01 | 콘티넨탈 테베스 아게 운트 코. 오하게 | Method for the decoupled control of the quadrature and the resonance frequency of a micro-mechanical rotation rate sensor by means of sigma-delta-modulation |
JP5516391B2 (en) * | 2010-12-24 | 2014-06-11 | トヨタ自動車株式会社 | Servo type capacitive sensor device |
CN106871887B (en) * | 2015-12-10 | 2020-02-18 | 上海矽睿科技有限公司 | Vibration module and gyroscope |
US11112269B2 (en) * | 2018-07-09 | 2021-09-07 | Analog Devices, Inc. | Methods and systems for self-testing MEMS inertial sensors |
US11255670B2 (en) | 2019-06-26 | 2022-02-22 | Stmicroelectronics, Inc. | MEMS gyroscope self-test using a technique for deflection of the sensing mobile mass |
US11162790B2 (en) * | 2019-06-26 | 2021-11-02 | Stmicroelectronics, Inc. | MEMS gyroscope start-up process and circuit |
US11175138B2 (en) | 2019-06-26 | 2021-11-16 | Stmicroelectronics, Inc. | MEMS gyroscope control circuit |
US11320452B2 (en) | 2019-06-26 | 2022-05-03 | Stmicroelectronics, Inc. | MEMS accelerometer self-test using an active mobile mass deflection technique |
EP3957953A1 (en) | 2020-08-19 | 2022-02-23 | Aptiv Technologies Limited | System and method for self-test of inertial measurement unit (imu) |
DE102020211467A1 (en) * | 2020-09-11 | 2022-03-17 | Robert Bosch Gesellschaft mit beschränkter Haftung | Circuit for a MEMS gyroscope and a method for operating a corresponding circuit |
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2005
- 2005-06-07 US US11/160,062 patent/US20050268716A1/en not_active Abandoned
- 2005-06-08 EP EP05759679A patent/EP1761739A1/en not_active Withdrawn
- 2005-06-08 JP JP2007527709A patent/JP2008501981A/en not_active Withdrawn
- 2005-06-08 WO PCT/US2005/020234 patent/WO2005121705A1/en not_active Application Discontinuation
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US5889193A (en) * | 1994-12-29 | 1999-03-30 | Robert Bosch Gmbh | Device for ascertaining a rate of rotation |
US6205838B1 (en) * | 1996-12-19 | 2001-03-27 | Robert Bosch Gmbh | Device for determining the rotational speed |
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Also Published As
Publication number | Publication date |
---|---|
US20050268716A1 (en) | 2005-12-08 |
JP2008501981A (en) | 2008-01-24 |
EP1761739A1 (en) | 2007-03-14 |
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